Tanks are sealed enclosures used to store fuel and other fluids prior to being withdrawn for use in industrial processes. One example is a gas tank for an internal-combustion engine, where gasoline is stored before being drawn into a fuel system and vaporized into ignitable fuel for combustion by the engine. In the case of cryogenic fuels, double-walled tanks are often used, comprising an inner enclosure for holding liquefied fuel, and an outer enclosure surrounding the inner enclosure to form an insulation space. The insulation space can be kept at a vacuum level to prevent, or at least reduce, heat transfer with the fuel, which in turn prevents, or at least reduces vaporization to keep the fuel in a liquefied state. For some applications the tank and/or insulation space can be maintained under a positive pressure. A vacuum rated plug can be used to seal the tank contents or maintain the insulation space at the vacuum level. The plug can also be rated for maintaining a positive pressure. Over time however, the plug can require servicing due to scratches, indentations and/or wear and tear on its seals. Servicing the plug can require removing it from the tank. Current methods for removing a vacuum rated plug, involve pressurizing the tank with nitrogen gas, and pulling the plug in atmosphere, which exposes the tank and its contents to external contaminants and compromises the vacuum level in the tank. Analogous methods can be used to service a positive pressure rated plug in that the pressure within the tank can be brought to atmosphere prior to the plug being pulled, which exposes the tank and its contents to external contaminants.